Why single inheritance??

[Sinex]

Hi,
Why does C# disallow multiple inheritance? Whats the reason behind this?
Is there any advantage or is it just a method to avoid some problems (if so,
what problems?) that come with multiple inheritance?

regards,
Sinex

[Manish Agarwal]

In very simple words-

To make design simpler

For details discussion have a look on http://tinyurl.com/36bzy

--------------------------------------------
Manish Agarwal <ma***********@ hotmail.com>
http://personal.vsnl.com/mkag

"Sinex" <ma************ @honeywell.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi,
Why does C# disallow multiple inheritance? Whats the reason behind this?
Is there any advantage or is it just a method to avoid some problems (if so, what problems?) that come with multiple inheritance?

regards,
Sinex

[Skyler York]

Interfaces were introduced as an alternative to multiple inheritance.
While you can only inherit from a single base class, you can implement
as many interfaces as you want.

[John Wood]

A lot of people say that if you're using multiple inheritence, then you're
design is probably messed up. While it is debatable, usually if you think
about it a bit you can find a neater (better?) way of achieving what you're
doing without using multiple inheritence.

Interestingly though, it's not like the CLR cannot support multiple
inheritence. Smalltalk achieves this under the CLR, but using a form of
aggregation (delegation) to achieve it. And I'm sure any attempt to use
these objects in other languages will show just how messy the implementation
of multiple inheritence is (I imagine you'll be going through member
variables to get to the parent classes). I believe Eiffel supports multiple
inheritence this way also.

--
John Wood
EMail: first name, dot, second name at priorganize.com
"Sinex" <ma************ @honeywell.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi,
Why does C# disallow multiple inheritance? Whats the reason behind this?
Is there any advantage or is it just a method to avoid some problems (if so, what problems?) that come with multiple inheritance?

regards,
Sinex

[Jon Skeet [C# MVP]]

John Wood <sp**@isannoyin g.com> wrote:

Interestingly though, it's not like the CLR cannot support multiple
inheritence. Smalltalk achieves this under the CLR, but using a form of
aggregation (delegation) to achieve it.
That's not the CLR supporting it though - that's Smalltalk effectively
emulating it. It's like claiming that the x86 supports the Z80
instruction set, just because there are Spectrum emulators available :)

The CLR cannot itself support multiple inheritence, IMO.
And I'm sure any attempt to use
these objects in other languages will show just how messy the implementation
of multiple inheritence is (I imagine you'll be going through member
variables to get to the parent classes).
Exactly.
I believe Eiffel supports multiple
inheritence this way also.

Yup, I believe so.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Michael Voss]

John Wood wrote:

Interestingly though, it's not like the CLR cannot support multiple
inheritence. Smalltalk achieves this under the CLR, but using a form of
aggregation (delegation) to achieve it.

Can you tell which Smalltalk dialect uses the CLR and offers multiple
inheritance ?

[John Wood]

Check out http://www.smallscript.org/ for more info.

--
John Wood
EMail: first name, dot, second name at priorganize.com
"Michael Voss" <mi**********@l vrREMOVE.deCAPS > wrote in message
news:40d84611$1 @news...

John Wood wrote:

Interestingly though, it's not like the CLR cannot support multiple
inheritence. Smalltalk achieves this under the CLR, but using a form of
aggregation (delegation) to achieve it.

Can you tell which Smalltalk dialect uses the CLR and offers multiple
inheritance ?

[Sahil Malik]

Just my opinion - Multiple inheritance in C++ was nothing but a pain in the
booty. I am glad C# didn't allow it. Although, I believe they were trying to
make a language not as difficult / lower entry level than C++. Another such
language is Java. It has 99.9999% of what you need, and only leaves the
complex parts out. IMHO that's sensible - it leads to better code and
cheaper programmers.

Specifically what problems could Multiple Inheritance cause in .NET. .NET
has somethign called as 'fixed object reference' that is - object references
to the one object in refer to same pointer value regardless of the type that
the reference is being interpreted as. For multiple inheritance, you would
loose that and along with you would loose all base type
interpretations/castings to base types. Secondly, you would loose all highly
efficient pointer comparisons. Yes you have the unsafe block, but who uses
it anyway when it says in red lettering "unsafe" (I had totally forgotten
about "unsafe", until I was reminded of it in these groups). But, shallow
cloning, equality reference etc. none would be as straightforward if you
didn't have fixed object references. Also, for all practical purposes that
MI can be used for, interfaces can do the same, albeit with too many vtable
jumps (3 compared to 1) so it is not as efficient .. but for cleaner code
and better readability, I can live with that.

- Sahil Malik
Independent Consultant
You can reach me thru my blog - http://dotnetjunkies.com/WebLog/sahilmalik/

"Sinex" <ma************ @honeywell.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi,
Why does C# disallow multiple inheritance? Whats the reason behind this?
Is there any advantage or is it just a method to avoid some problems (if so, what problems?) that come with multiple inheritance?

regards,
Sinex

[John Wood]

>> 'fixed object reference' that is - object references to the one object in
refer to same pointer value regardless of the type that the reference is
being interpreted as <<

wha? :)

--
John Wood
EMail: first name, dot, second name at priorganize.com
"Sahil Malik" <no****@ms.co m> wrote in message
news:%2******** *******@TK2MSFT NGP12.phx.gbl.. .

Just my opinion - Multiple inheritance in C++ was nothing but a pain in the booty. I am glad C# didn't allow it. Although, I believe they were trying to make a language not as difficult / lower entry level than C++. Another such language is Java. It has 99.9999% of what you need, and only leaves the
complex parts out. IMHO that's sensible - it leads to better code and
cheaper programmers.

Specifically what problems could Multiple Inheritance cause in .NET. .NET
has somethign called as 'fixed object reference' that is - object references to the one object in refer to same pointer value regardless of the type that the reference is being interpreted as. For multiple inheritance, you would
loose that and along with you would loose all base type
interpretations/castings to base types. Secondly, you would loose all highly efficient pointer comparisons. Yes you have the unsafe block, but who uses
it anyway when it says in red lettering "unsafe" (I had totally forgotten
about "unsafe", until I was reminded of it in these groups). But, shallow
cloning, equality reference etc. none would be as straightforward if you
didn't have fixed object references. Also, for all practical purposes that
MI can be used for, interfaces can do the same, albeit with too many vtable jumps (3 compared to 1) so it is not as efficient .. but for cleaner code
and better readability, I can live with that.

- Sahil Malik
Independent Consultant
You can reach me thru my blog - http://dotnetjunkies.com/WebLog/sahilmalik/
"Sinex" <ma************ @honeywell.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi,
Why does C# disallow multiple inheritance? Whats the reason behind this? Is there any advantage or is it just a method to avoid some problems (if

so,

what problems?) that come with multiple inheritance?

regards,
Sinex

[Greg Young]

ok everyone seems to have had their word ... Let me approach this
differently.

How is single inheritance with interfaces any different than multiple
inheritance where you only inherit 1 non-pure and many pure abstract bases ?

Many people have suggested that this can be considerred good practice in
multiple inheritance as well since it creates simpler sometimes more
flexible code (per bad design of default behaviors) and good programmers are
expensive. The cost of the simpler code is the ability to provide default
behaviors in your many pure abstracts, if you are designing properly this
will probably not be a major issue.

Cheers,

Greg

"Sinex" <ma************ @honeywell.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi,
Why does C# disallow multiple inheritance? Whats the reason behind this?
Is there any advantage or is it just a method to avoid some problems (if so, what problems?) that come with multiple inheritance?

regards,
Sinex